Alternatively, provided something cold, to help with cavity (7)
I believe the answer is:
orifice
'cavity' is the definition.
(thesaurus)
'alternatively provided something cold' is the wordplay.
'alternatively' becomes 'or'.
'provided' becomes 'if' (eg 'provided it's sunny' means 'if it's sunny').
'something cold' becomes 'ice'.
'or'+'if'+'ice'='ORIFICE'
'to help with' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for orifice that I've seen before include "Bodily opening, mouth of cavity" , "8 [OPENING]" , "Hole in the head, perhaps?" , "Aperture" , "Mouth-like opening" .)